Hysteresis compensator



Dec. 12, 1944. w A, RAY 2,364,917

V nyswsm asis COMP'ENSATOR Filed Dec. 1, 1941 4 1 I Zinventor: W/u/AM A.RAY,

(Ittorneg Patented Dec. 12, 1944 2,364,917 nrs'reassrs comrnmsa'roaWilliam A. Ray, Los Angeles, Calif;

Application December 1, 1941', Serial No. 421,179

7 Claims.

My present invention relates to hysteresiscompensating means andparticularly to such means of the type adaptedto reduce delay indrop-out" of an armature upon deenergization of its electromagnet.

In electromagneticaliy controlled devices in which an armature isattracted through a distance against a biasing force, theelectromagnetic force required to move the armature through space ismuch greater than that then required to hold the armature in itsattracted position. Thus there necessarily is a large differentialbetween the electromagnetic force and the opposing biasing force duringthe attracted movement of the armature.

In control systems employing a thermoelectric generator for energizationof the electromagnet,

upon failure of the means for heating the gen-- erator, currentcontinues to flow, in a gradually decreasing amount, which current,until the' differential between the electromagnetic force and thebiasing force is overcome, will be eflfective to retain the armature inits attracted posi-- tion. With such a gradual deenergization of theelectromagnet, and with a large differential be-' is in its attractedposition, while maintaining a It is therefore an object of thisinvenwill be found in the description, the drawing and the appendedclaims; and for complete understanding of the invention, reference maybe had to the following detailed description and accompanying drawing,wherein;

Figure. 1 is adiagrammatic representation of a controlsystem embodyingmy invention; and

Figure 2 is a similar representation of a system embodying amodifledform of my invention.

In the drawing, the numeral Ii indicates a valve casing having an inletl2 and an outlet I3 separated by a ported partition l4 providing a mainvalve seat l5. Cooperable with the seat I! is a closure member iscarried by a diaphragm I! which is arranged to cover an opening in thetop of the casing. The diaphragm is held at its margin between flangedportions of casing Ii and of a housing l8, secured to the casing toprovide a pressure chamber l9 above the diaphragm.

For controlling the fl-uid pressure in chamber IS, .a three-way valve isprovided which comprises a pair of jet members 20 and 2i. Jet member 20is connected with the inlet l2 by a pipe 22, and jet 2! communicateswith the atmosphere through a pipe 23 extending through a side wall ofthe housing. Cooperabie with jets 20 large differential between theforces when in its ture toward the electromagnet for increasing thearmature-biasing force.

Another object is to provide, in a device of the and 2| is an armature24, fulcrumed at a point intermediate its length'on one leg of aU-shaped electromagnet core 25 and urged by a compression spring 26 to aposition wherein jet 2| is closed.

thermostat 29 to a thermoelectric generating device 30, adapted to beheated by a flame 3i of a burner 32. When the thermostat 29 is incircuit-open position, the electromagnet is unenergized and spring 26holds armature 24 in engagetype indicated, means actuated in response tothe movement of the armature toward the electromagnet for decreasing theelectromagnetic.

such that-a relatively large amount of flux is employed for attractionof the armature, as when a large air gap initially exists between thearmature and electromagnet, the residual magnetism may then be so greatthat there is a tendency for the armature to hang-up" even when theelectromagnetic circuit is, abruptly opened.

Other objects and advantages of my invention the diaphragm; the partsbeing in the positions shown in Fig. 1.

Upon closing of the energizing circuit by the thermostat 29, theelectromagnet will attract the armature 24 and move it, against theforce of spring 26, to a position wherein jet 2| is open and Jet 20 isclosed. The parts are so positioned that the armature closelyapproachesbut never actually contacts the. upper leg of the core 25, sothat proper engagement of the armature with the let 2| is assured. Withthe armature in its attracted mitting the pressure below it to raise thedia-.

phragm against the weight of disk 33. The closure I6 is thus moved toits open position, allowing fluid to pass from the inlet I 2 to theoutlet l2. Subsequent deenergization of the electromagnet will permitspring 26 to move armature 24 to the position wherein jet 2| is againclosed, whereby fluid may enter chamber I! through pipe 22. As thepressures above and below the diaphragm equalize, weight I2 again forcesclosure member it'into engagement with its seat.

A bucking coil 34 is connected by wires 4. in parallel with the maincoil 21 through a mercurytube switch 35, and is reversely wound on thecore 25 to produce, when energized, a magnetic flux opposing that of themain coil but of lesser magnitude. The switch is secured on an arm 38which is pivoted at one of its ends on a portion of the housing It, thearm being connected toward its other end with the disk 33 by a link 21.

when the closure member i6 is in engagement with its seat i 5, the arm28, on which the switch is secured, is at such an angle that the mercury28 is separated from the contacts 38. Thus, when the main coil 21 isinitially energized, the bucking coil 34 is not energized, and themaximum force of the electromagnet is available to attract the armature24. However, after the armature is in its attracted position, thediaphragm l1 starts to rise, as previously described, and causes theswitch 35 to tilt to such an angle that the mercury flows toward thecontacts and bridges the same. This causes energization of the buckingcoil 34, and the magnetic flux tending to hold the armature in itsattracted position is thereby reduced, but is still of suillcientmagnitude to hold the armature in its attracted position against theopposing force of spring 26. It

will be seen that by thus decreasing the difleren-- tial between theelectromagnetic force and the spring force, less decrease in theelectromagnetic flux is required to allow the armature to dropout thanwould be the case with a large diilerential between these forces. Theundesirable holdin" effects, produced by residual magnetism or gradualdeenergization of the electromagnet, are thus overcome.

In Fig. 2 of the drawing is shown an embodiment oi my invention in whichmechanical means are employed to vary the effective, or resultant, forcetending to hold the armature in its attracted position. Compressedbetween the armature 24 and one arm of a pivotally mounted bell-crank 4|is a spring 42, constantly urging the armature away from theelectromagnet. The other arm of the bell-crank is connected by a link 43to an arm 44 which is pivotally mounted at one of its ends on a portionf the housing It. The other end of the arm 44 is in slidable engagementwith the top surface of the disk 33. When the closure member I6 is inengagement with the seat i5, upon initial energization of theelectromagnet the armature is moved toward the core 25 against the forceof spring 42. This results in upward movement of the diaphragm, aspreviously described, and similar movement of the free end of pivotedarm 44. The movement of this arm is transmitted through link 43 to thebell-crank 4i which turns in an anticlockwise direction to furthercompress spring 42, whereby the differential between the magneticholding force and the opposing spring force is reduced.

While I have herein shown and described, by way of illustration,specific embodiments of my invention, I wish it to be understood thatmodiilcations may be made without departing from the spirit of theinvention, and that I intend therefore to be limited only by the scopeof the appended claims.

I claim as my invention:

1. In a control system: a motor movable between limiting positions; anelectromagnet; an armature movable toward the electromagnet, when thesame is energized, to a position wherein the reluctance of the magneticcircuit, formed by the electromagnet and the armature, is reduced; meansconstantly urging the armature away from the electromagnet; meansactuated by the movement of the armature for so controlling theoperation of said motor that it moves directly from one of its limitingpositions to the other; and means for facilitating movement of thearmature away from the electromagnet when the same is deenerglzedcomprising means independent of the armature and controlled by themovement of the motor, in response to the movement of the armaturetoward the electromagnet, for decreasing the resultant force thentendingto retain the armature in its attracted position.

2. In a control system': a motor, and electro magnetic means forcontrolling the operation of said motor; said electromagnetic meanscomprising an electromagnet and an armature cooperable therewith, saidarmature being movable toward said electromagnet when the same isenergized to a position wherein the reluctance of the electromagneticcircuit is reduced, means urging the armature away from theelectromagnet, and means controlled by the movement of said motor inresponse to the movement of the armature toward the electromagnet fordecreasing the force applied to the armature by the electromagnet.

3. In a control system: a fluid pressure operated motor andelectromagnetic means for controlling the operation of said motor; saidelectromagnetic means comprising an electromagnet and an armaturecooperable therewith, said electromagnet said main coil, said armaturebeing movable toward said electromagnet when said main coil is energizedto a position wherein the reluctance of the electromagnetic circuit isreduced, means constantly urging the armature away from theelectromagnet, and switching means controlled by the movement of saidmotor in response to the movement of said armature toward theelectromagnet for connecting said bucking coil to a source of electricalenergy.

4. A control system as defined in claim 1: wherein said armature-urgingmeans is a spring; and the'means, controlled by'the movement of themotor for decreasing the resultant force tending to retain the armaturein its attracted position, consists of means for increasing the-force ofsaid spring. I

5. A control system as defined in claim 1: wherein said armature-urgingmeans is a spring; and the means, controlled by the movement of themotor for decreasing the resultant force tending to retain the armaturein its attracted position, consists of a lever mechanism sointerconnecting said motor and said spring that the force of the same isincreased.

. 6. In a control system: an electromagnet having a main energizing coiland a bucking coil,

said bucking coil being effective when energized to oppose and partiallyovercome the effect of said main coil, a thermoelectric generator forenergizing said main coil, means for heating said generator, an armaturemovable toward said electromagnet when said main coil is energized,means urging said armature away from the electromagnet, a motorcontrolled by the movement of the armature, and means controlled by themovement of said motor in response to the movement 10 of the armaturetowards the electromagnet for assuring prompt release of the armatureupon failure of said heating means, said motor-com trolled meanscomprising means for connecting said bucking ooil to a source ofelectrical energy. 7. A control system as defined in claim 1:whereinsaid motor is of the fluid pressure oper-' ated type, and themeans actuated by the movement of the armature is a pilot valve.

WILLIAM A. RAY.

